Cable connectors

ABSTRACT

A connection for coaxial cables, which provides reduced return losses and is particularly suitable for cables having corrugated outer conductors. The connection maintains the inner diameter of the outer conductor substantially constant across the joint. A ferrule having an inner sleeve which is expanded to grip the outer conductor between the inner sleeve and an outer sleeve provides good mechanical and electrical connection to the outer conductor. A central tubular member, split into opposed halves, surrounds the joint between the inner conductors and nuts screw on the ends of the tubular member to connect the ferrules to the central tubular member.

United States Patent Zimmermann et al.

[ June 27, 1972 [54] CABLE CONNECTORS Canada [73] Assignee: Northern Electric Company Limited, Montreal, Quebec, Canada [22] Filed: Feb. 22, 1971 21 Appl. No.: 117,524

[52] US. Cl. ..l74/88 C, 29/628, 174/89,

174/92, 339/89 C, 339/l77 R [51] Int. Cl. ..H02g 15/08 [58] Field of Search ..l74/75 C, 88 C, 89, 21 C, 35 C,

174/35 SM, 9l-93; 339/276 R, 89 R, 89 C, 90 C, 177 R, 177 E; 29/628, 629

Davies ..l74/35 C UX Colussi ..l74/88 C X Primary Examiner-Darrell L. Clay Attorney-Sidney T. Jelly 51 ABSTRACT A connection for coaxial cables, which provides reduced return losses and is particularly suitable for cables having corrugated outer conductors. The connection maintains the inner diameter of the outer conductor substantially constant across the joint. A ferrule having an inner sleeve which is expanded to grip the outer conductor between the inner sleeve and an outer sleeve provides good mechanical and electrical connection to the outer conductor. A central tubular member, split into opposed halves, surrounds the joint between the inner conductors and nuts screw on the ends of the tubular member to connect the ferrules to the central tubular member.

8 Claims, 5 Drawing Figures Patented Jme 27, 1972 3,673,314

2 Sheets-Sheet 1 INVENTORS 42 4| A DETLEF ZIMMERMANN DAVID CAMPBELL F 5 GEORGE DE BORTOLI BY L. 269/ PATENT AGENT Patented June 27, 1972 3,673,314

2 Sheets-Sheet Z Fig. 2

2D\W |9 zo Fig. 3

INVENTORS DETLEF ZIMMERMANN DAVID CAMPBELL GEORGE DE BORTOLI BY C PATENT AGENT CABLE CONNECTORS This invention relates to connections for coaxial cables, and particularly to splicing coaxial cables to provide reduced return losses. The invention can be used to join opposed ends of lengths of similar cable, or to join one end of a coaxial cable to a further connector.

In particular the invention is concerned with coaxial cables in which the outer conductor is in the form of a corrugated tube, although the invention can be used for other forms of tubular outer conductors.

The invention provides a splice, or joint, in which the inner dimensions of the outer conductor can be maintained substantially constant across the splice, or joint.

Various forms of splicing exist. For example, the outer conductors can be joined by crimping, but a variation in dimensions of the conductor results. Similarly crimping of the inner conductor is used but-with the same undesirable effects. In another particular form, the outer and inner conductors are butt brazed after the outer conductor has been opened up and flattened. The outer conductor is then reformed into a tube around the inner conductor after brazing. This latter form of splice is suitable for an outer conductor produced by a strip formed into a tube, but with the seam unsealed. For a tubular conductor formed from a solid tube, or seamed tube, opening and flattening of the tube is at least unsatisfactory and is generally impracticable.

The present invention provides means for splicing or joining coaxial cables in which the inner dimensions of the outer conductor are maintained substantially constant across the splice or joint, the splice or joint being easily made and meeting high standards of return loss requirements and is also of high mechanical strength. A splice, or joint, in accordance with the present invention has the added feature that it can be taken apart easily for inspection or other purposes.

' In accordance with the present invention there is provided a connection for a coaxial cable having an inner conductor and an outer tubular conductor, comprising; a ferrule having an outer sleeve for positioning over the exterior of the outer conductor and an inner sleeve for positioning inside the outer conductor, the inner sleeve adapted for expansion to grip the outer conductor between the inner and outer sleeves; a central body member comprising a tubular member divided longitudinally into at least two sections; and means for engagement with the ferrule and the central body member for connecting the ferrule and the central body member.

Generally, the means engaging the ferrule and the central body member comprises a nut which screws on to the end of the central body member urging the ferrule into endto-end contact with the central body member.

For a splice, or joint, for opposed ends of cables, a ferrule and nut are provided at each end of the central body member. The central body member may be straight or may have two portions at an angle at each other, for example at right angles.

The invention will be understood by the following description of certain embodiments, by way of example, in conjunction with the accompanying drawings, in which:

FIG. 1 is a longitudinal cross-section through a splice, or joint, connecting opposed ends of two coaxial cables;

FIG. 2 is an exploded perspective view of a splice, or joint, as illustrated in FIG. 1;

FIG. 3 is a longitudinal cross-section of a ferrule before expanding on to an outer conductor;

FIG. 4 is a cross-section, normal to the longitudinal axis, of one section of a central body member; and

FIG. 5 is a cross-section, on the longitudinal axis, of a central body member for a right-angled splice or joint.

As seen in FIGS. 1 and 2, a first coaxial cable has an inner conductor 11 and an outer tubular conductor 12. A second coaxial cable 13 has an inner conductor 14 and an outer tubular conductor 15. In the embodiment shown, the outer conductors 12 and Bare corrugated. The inner conductors 11 and 14 are maintained in a central spaced relationship with outer conductors 12 and 15 by insulating discs 16.

The end of each outer conductor 12, 15 is gripped in a ferrule 17, illustrated in more detail in FIG. 3.

As shown in FIG. 3, each ferrule 17 comprises an inner sleeve 18 and an outer sleeve 19. For the major portion of its length the bore 20 of the outer sleeve 19 is of a diameter to fit closely on the exterior of the outer conductors l2 and 15. At one end of the bore is reduced in diameter, at 21 and provides an end stop against which the end of the related outer conductor abuts. Initially the major portion 22 of the inner sleeve 18 is of a diameter which will readily enter the bore of the outer conductors 12 and 15. At one end however, a short length 23 is a fairly tight push-fit in the reduced diameter portion 21 of the outer sleeve 19. The inner sleeve 17 also has a flange 24 at the end of the portion 23, which flange is intended to abut the end of the outer sleeve 18. A small hole 25 may be formed in the outer sleeve 18 so that the correct insertion of the outer conductor into the outer sleeve can be checked.

Referring again to FIGS. 1 and 2, a central body member 30 is positioned between the opposed ends of the outer conductors l2 and 15. In the embodiment illustrated, the central body member 30 is divided longitudinally into two sections 31. The central body member 30 is externally threaded at each end, at 32. A nut 33 is provided on each cable, each nut having an internally threaded portion 34 at one end for engagement with the related threaded portion 32 of the central body member 30. At the end remote from the threaded portion 34 each nut has an inwardly extending flange 35. In position the flanges 35 engage the ends of the ferrules l7 urging the ferrules into contact with the ends of the central body member 30.

FIG. 4 illustrates, in cro's-section, one of the sections 31 forming the central body member 30. In the embodiment illustrated in FIGS. 1 and 2, the central body member 30 is formed by two sections 31 which are substantially identical. As seen in FIG. 4 each section 31 is of semi-cylindrical form. Two sections 31 abut on opposed longitudinal edges 36. Extending along each edge 36 is a slot 33. The slots 33 extend almost the full length of the edges 36, finishing just short of each end of the section. In one of the slots is positioned a metal strip 37. Strips 37 are preferably a tight fit in one slot and may be permanently fixed in position, as by soldering or brazing. The strips 37 are positioned so that the sections 31 can be assembled with the strip in one section cooperating with a slot in the other section. If desired both the strips can be fixed in one section, but generally one strip is in each section. The provision of the strips 37 prevents cross-talk between adjacent splices. In addition, the strips 37 assist in assembly of the sections assuming alignment thereof and particularly of the threaded end portions. In an alternative form the sections 31 are cast or molded, and the strips 37 should then be formed as a solid extension in one with a section. Strips such as 37 may not be required in all instances.

To make a splice, or joint, the outer conductor is cut back to expose a predetermined length of internal conductor. A nut 33 is then passed over the end of each cable, over the end of each external conductor. A ferrule 17 is then positioned over the end of each outer conductor. An expanding tool is then pushed through the inner sleeve, enlarging the bore portion 22 to substantially the same internal diameter as the portion 23. This enlargement causes collapse of the corrugations of the outer conductor and a firm effective attachment of the conductor to the ferrule is made, joining good electrical contact and mechanical strength.

After expansion of the inner sleeves 18, the opposed ends of the inner conductor are butted together and brazed. It is necessary to ensure that the exposed lengths of the inner conductors are such that when the inner conductors are brazed, the distance between the opposed ends of the ferrules 17 is equal to the length of the central body member 30. After brazing of the inner conductors, the sections 31 of the central body member 30 are assembled around the splice, or joint, and the nuts 33 screwed on to the central body member 30, forcing the ferrules 17 into contact with the ends of the central body member 30. Additional spacing insulating means, such as discs 16, can be positioned inside the central body member to maintain correct positioning of the inner conductor. Instead of separate discs, a molded or other form of spacing member may be provided.

Thus it will be seen that there is provided a connector for a splice or joint, having high electrical and mechanical efficiency, which gives very good return loss results, and is readily taken apart for inspection purposes.

FIG. 5 illustrates a modified embodiment, giving an angled splice, or joint; in the particular example illustrated a right-angle. FIG. 5 illustrates only the central body member 40, which is composed of two sections, with externally threaded end portions 41. Slots 42 are provided, and a strip 43 is provided in each section. Fer-rules and nuts as in the embodiment illustrated in FIGS. 1 and 2 are used to connect the outer conductors at each end of the central body member 40.

The invention can also be used to connect a coaxial cable to a coaxial connector, such as a jack. Such an arrangement would be similar to that illustrated in FIGS. 1 and 2, or as modified in FIG. 5, with the variation that instead of the second cable, for example cable 13, the central body member 30, or 40, would be attached to the connector. A nut, similar to the nuts 33, would be used to connect the connector at one end of the central body member.

Although the invention has been described in relation to a cable having a corrugated outer conductor it can also be used for other forms of outer conductor, for example a smooth tubular conductor. The inner sleeves 22 of the ferrules 17 are expanded sufficiently to grip the outer conductor between the sleeves. If necessary some roughening or profiling of the outer surface of the inner sleeve, and the inner surface of the outer sleeve, can be provided to improve the mechanical strength of the attachment of the ferrule to the outer conductor.

What is claimed is:

l. A coaxial cable connection, said cable having an inner conductor and an outer tubular conductor, comprising:

a central body member comprising a tubular member divided longitudinally into at least two sections and positioned around a joint between the inner conductors;

a ferrule having an inner sleeve and an outer sleeve, the

outer sleeve positioned over the exterior of the outer conductor, the inner sleeve positioned inside the outer conductor and expanded to grip the outer conductor between the inner and outer sleeves; and

a nut having a threaded portion in engagement with a threaded portion on said central body member and a flange in engagement with the ferrule to connect the ferrule and the central body member.

2. A coaxial cable connection joining two coaxial cables, each cable having an inner conductor and an outer tubular conductor, comprising:

a central tubular body member divided longitudinally into two opposed halves and positioned around the joint between the two inner conductors;

a first ferrule attached to the end of one outer conductor and a second ferrule attached to the end of the other outer conductor, each ferrule including an inner sleeve and an outer sleeve, the outer sleeve positioned over the exterior of the related outer conductor, the inner sleeve positioned inside the related outer conductor and expanded to grip the outer conductor between inner and outer sleeves; and

means in engagement with the ferrules and the opposed ends of the central member connecting the ferrules to the central member, one on each end, said means comprising nuts, a threaded portion in engagement with a threaded end portion on said central body member and a flange in engagement with the related ferrule.

3. A connection as claimed in claim 2, wherein said central member is a straight member.

4. A connection as claimed in claim 2, wherein said central member has two rtions extending at an an le at each other.

5. A method 0 connecting a coaxial cab e having an inner conductor and an outer tubular conductor, comprising the steps of; positioning an outer sleeve on the end of the outer conductor; inserting an inner sleeve inside the end of the outer conductor; expanding the inner sleeve to grip the outer conductor between the sleeves, said sleeves forming a ferrule; positioning a central tubular member about the inner conductor; and connecting said ferrule to the central member by connecting means engaging with said ferrule and said central member. 7

6. A method of connecting two opposed ends of coaxial cables having an inner conductor and an outer tubular conductor, comprising the steps of:

cutting back the outer conductor on each cable to expose a predetermined length of inner conductor;

positioning a nut on each outer conductor;

positioning an outer sleeve on the end of each outer conductor;

inserting an inner sleeve inside the end of each outer conductor;

expanding each inner sleeve to grip the outer conductors between inner and outer sleeves, each cooperating inner and outer sleeve forming a ferrule;

joining the opposed ends of the inner conductors to form a continuous conductor;

positioning a central tubular member about the inner conductor;

screwing the nuts onto the ends of the central member to connect the ferrules to the central member.

7. A method as claimed in claim 6, wherein the outer eonductor is of corrugated form and each inner sleeve is expanded to collapse the corrugations of the outer conductor.

8. A method as claimed in claim 6 wherein each inner sleeve is expanded to an internal diameter substantially equal to the minimum internal diameter of the outer conductor.

i i i i l 

1. A coaxial cable connection, said cable having an inner conductor and an outer tubular conductor, comprising: a central body member compriSing a tubular member divided longitudinally into at least two sections and positioned around a joint between the inner conductors; a ferrule having an inner sleeve and an outer sleeve, the outer sleeve positioned over the exterior of the outer conductor, the inner sleeve positioned inside the outer conductor and expanded to grip the outer conductor between the inner and outer sleeves; and a nut having a threaded portion in engagement with a threaded portion on said central body member and a flange in engagement with the ferrule to connect the ferrule and the central body member.
 2. A coaxial cable connection joining two coaxial cables, each cable having an inner conductor and an outer tubular conductor, comprising: a central tubular body member divided longitudinally into two opposed halves and positioned around the joint between the two inner conductors; a first ferrule attached to the end of one outer conductor and a second ferrule attached to the end of the other outer conductor, each ferrule including an inner sleeve and an outer sleeve, the outer sleeve positioned over the exterior of the related outer conductor, the inner sleeve positioned inside the related outer conductor and expanded to grip the outer conductor between inner and outer sleeves; and means in engagement with the ferrules and the opposed ends of the central member connecting the ferrules to the central member, one on each end, said means comprising nuts, a threaded portion in engagement with a threaded end portion on said central body member and a flange in engagement with the related ferrule.
 3. A connection as claimed in claim 2, wherein said central member is a straight member.
 4. A connection as claimed in claim 2, wherein said central member has two portions extending at an angle at each other.
 5. A method of connecting a coaxial cable having an inner conductor and an outer tubular conductor, comprising the steps of; positioning an outer sleeve on the end of the outer conductor; inserting an inner sleeve inside the end of the outer conductor; expanding the inner sleeve to grip the outer conductor between the sleeves, said sleeves forming a ferrule; positioning a central tubular member about the inner conductor; and connecting said ferrule to the central member by connecting means engaging with said ferrule and said central member.
 6. A method of connecting two opposed ends of coaxial cables having an inner conductor and an outer tubular conductor, comprising the steps of: cutting back the outer conductor on each cable to expose a predetermined length of inner conductor; positioning a nut on each outer conductor; positioning an outer sleeve on the end of each outer conductor; inserting an inner sleeve inside the end of each outer conductor; expanding each inner sleeve to grip the outer conductors between inner and outer sleeves, each cooperating inner and outer sleeve forming a ferrule; joining the opposed ends of the inner conductors to form a continuous conductor; positioning a central tubular member about the inner conductor; screwing the nuts onto the ends of the central member to connect the ferrules to the central member.
 7. A method as claimed in claim 6, wherein the outer conductor is of corrugated form and each inner sleeve is expanded to collapse the corrugations of the outer conductor.
 8. A method as claimed in claim 6 wherein each inner sleeve is expanded to an internal diameter substantially equal to the minimum internal diameter of the outer conductor. 